I took the single lever faucet handle cartridge out of the bathtub faucet thinking that that was the cause of the constant drip, drip, drip from the bathtub faucet. The showerhead above has never leaked and it doesn't now. I shut off the main water valve to the house before I started. I got the stem/cartridge completely out and THERE IS STILL A CONSTANT TRICKLE OF WATER COMING OUT OF THE PIPE IN THE WALL THAT THE STEM WENT INTO. Does this mean that the cartridge wasn't my original problem? There are two water heaters for my house. Does this mean there is a second main shut off somewhere that I didn't shut off before starting to take the faucet handle apart to get to the catridge? I have a towel stuffed into the pipe opening now because if I don't catch the dribble, it drips behind the wall. Do I need to call a plumber? Is this normal? If I just go out and buy a new cartridge and put it all back in the pipe will this stop my leaking? Any advice is greatly appreciated. Betsy